Strict conservation measures mean public access to Parque Nacional Caguanes with its caves, aboriginal remains and flamingos is limited but not impossible. There is a basic biological station on the coast accessible by a rough road due north of Mayajigua but, rather than just turn up, your best bet is to check details first at the Villa San José del Lago or with Ecotur, which has a handy public office in Trinidad.
The one advertised excursion is Las Maravillas que Atesora Caguanes (2½ hours), which incorporates a path to the Humboldt, Ramos and Los Chivos caves and a boat trip around the Cayos de Piedra.